igneous
Grey Basalt or Andesite with Veining
Intermediate to Mafic Extrusive Igneous Rock with Quartz/Calcite Veins
Hardness: 5-7 (Mohs), Color: Dark grey with tan/white veins, Luster: Dull to sub-vitreous, Structure: Aphanitic (fine-grained), Cleavage: None
Identified More igneous →
Explore Grey Basalt or Andesite with Veining in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-7 (Mohs), Color: Dark grey with tan/white veins, Luster: Dull to sub-vitreous, Structure: Aphanitic (fine-grained), Cleavage: None
Formation & geological history
Formed from the rapid cooling of lava at or near the Earth's surface. The lighter veins formed later, as mineral-rich fluids filled fractures in the solid rock.
Uses & applications
Commonly used in landscaping, as decorative stones, or as a source of crushed stone for construction and road building.
Geological facts
The smooth, rounded shape indicates it is likely a river rock or beach pebble, naturally polished by water erosion. The veins act as a geologic 'scar' from old tectonic activity.
Field identification & locations
Identified by its fine grain, dark grey color, and intersecting mineral veins. Found globally in volcanic regions and riverbeds. It will not react to acid unless the veins are calcite.
